The downturn in the rate of climate warming over the past decade does not significantly change estimates of the eventual (equilibrium) temperature rise in response to doubled atmospheric CO2 concentrations, according to a study published online this week in Nature Geoscience. However, the work suggests that the immediate temperature response to rising levels of greenhouse gases in the atmosphere - before an equilibrium is reached - may need to be revised downwards.
Alexander Otto and colleagues analysed observation-based estimates of surface temperatures and the Earth’s heat budget as well as radiative forcing estimates obtained from the historic record and climate model simulations. They use these data to determine ranges for the equilibrium climate sensitivity and the transient climate response to a doubling of CO2 concentrations between 1970 and 2009. The researchers find that most of the climate models used in the upcoming fifth assessment of the Intergovernmental Panel on Climate Change are consistent with the results presented, but they note considerable uncertainties.